1. Field of the Invention
The present invention relates to an electromagnetic actuator with a mechanical locking linkage and more particularly to an electromagnetic actuator with a mechanical locking linkage which prevents unintended movement of the actuator plunger into the well of the actuator.
2. Description of the Prior Art
Electromagnetic actuators convert electrical impulses into mechanical action and perform many functions. Specifically, in one application an electromagnetic actuator performs the latching and unlatching function in a locking mechanism. In such an application, the plunger of the electromagnetic actuator typically serves as a latching member which engages a corresponding member to secure the door or other movable structure used to close an opening.
The plunger of the solenoid device in this application moves along a generally vertical axis. It rises out of locking engagement under the force of magnetic flux generated by the actuator coil when the user energizes the coil. Upon removal of the power input, it drops, under the force of gravity, into locking engagement.
Maintaining the plunger in the raised position requires continuous energizing of the actuator. However, unlatching the locking device requires that the solenoid raise the plunger and maintain it in the raised position only a relatively short time duration. Thus, the user need only pulse the solenoid, minimizing the energy used by the solenoid.
Typically, the plunger lies in the lower position, i.e. in locking engagement, for a substantially longer time duration. To conserve energy, the locking mechanism relies on the weight on the plunger to maintain it in the lower position. But for this application, as well as most other applications, the plunger cannot have an excessive weight or size.
Due to the size and weight limitations, the actuators used in this application suffer a severe disadvantage where security is an important consideration. They cannot prevent tampering. A blow applied to the locking mechanism and directed so that it lifts the plunger allows unlatching of the locking mechanism.
The solenoid device of the present invention provides a mechanical linkage which allows the user to move the solenoid armature in and out of locking engagement; and it prevents tampering and unintended movement of the armature out of locking engagement. It provides a construction which minimizes the expense of manufacturer and assembly and gives precise, uniform and reliable performance. The solenoid device of the present invention comprises a small number of components with sufficiently accurate and consistent tolerances. These components produce the requisite mechanical action and place the armature in proper position and alignment yet prevent tampering or any undesired movement of the armature.